The present invention relates generally to growth of plants and algae and, more particularly, to the use of the chemical class of compounds known as prolines for improving the properties and performance of plants and algae.
Many agricultural activities are time sensitive, with costs and returns being dependent upon rapid turnover of crops or upon being first to reach the market place. Therefore, rapid plant growth is an economically important goal for many agricultural businesses that grow high-value crops such as vegetables, berries, and bananas, as well as for the greenhouse and nursery businesses. The importance of improved crop production technologies has increased as a result of the observation that yields for many well-developed crops have tended to plateau in recent years. The goal of rapid plant growth has been addressed in numerous studies of plant regulatory mechanisms, which remain incompletely understood. In particular, a complete understanding has not been attained for the plant regulatory mechanisms that coordinate carbon and nitrogen metabolism, which must have a major impact on plant growth and development.
The metabolism of carbon and nitrogen in photosynthetic organisms must be regulated in a coordinated manner to assure efficient use of plant resources and energy. Understanding of carbon and nitrogen metabolism now includes details of certain steps and metabolic pathways which are subsystems of larger systems. In photosynthetic organisms, carbon metabolism begins with CO2 fixation which includes two major processes termed C-3 and C-4 metabolism. In plants with C-3 metabolism the enzyme, ribulose bisphosphate carboxylase (RuBisCo) catalyzes the combination of CO2 with ribulose bisphosphate to produce 3-phosphoglycerate, a three carbon compound (C-3), that the plant uses to synthesize carbon-containing compounds. In plants with C-4 metabolism, CO2 is combined with phosphoenol pyruvate to form acids containing four carbons (C-4) in a reaction catalyzed by the enzyme phosphoenol pyruvate carboxylase. The acids are transferred to the bundle sheath cells where they are decarboxylated to release the CO2 which is then combined with ribulose bisphosphate in the same reaction as employed by C-3 plants. In photosynthetic organisms, nitrogen is assimilated by the action of the enzyme glutamine synthetase which catalyzes the combination of ammonia with glutamate to form glutamine.
Previous research focusing on important enzymes and the genes encoding for them has investigated the enzyme catalyzing the assimilation of nitrogen to form glutamine. One such study is xe2x80x9cModulation of Glutamine Synthetase Gene Expression In Tobacco by the Introduction of an Alfalfa Glutamine Synthetase Gene in Sense and Antisense Orientation: Molecular and Biochemical Analysisxe2x80x9d by Stephen J. Temple et. al., Mol. Gen. Genet 236, 315 (1993), the teachings of which are hereby incorporated by reference herein. Therein it is stated that plants overexpressing the glutamine synthetase (GS) gene were visibly greener than control plants. Although, GS1-overexpressing plants exhibited about 45% increase in total soluble protein and the GS1 antisense expressing plants exhibited about 40% decrease in total soluble protein, no mention was made of more rapid growth rate or greater plant yields. In xe2x80x9cOverexpression of a Soybean Gene Encoding Cytosolic Glutamine Synthetase in Shoots of Transgenic Lotus coroniculatus L. Plant Triggers Changes in Ammonium Assimilation and Plant Developmentxe2x80x9d by Remi Vincent et. al., Planta 201, 424 (1997), it is stated that a 50% to 80% increase in total leaf GS activity in transgenic plants is followed by degradation of shoot protein and early floral development. As these properties are characteristic of senescent plants, Vincent et al. states that the over expression of GS in shoots may accelerate plant development, thus leading to premature flowering and early senescence. Again, no mention is made of any increase in plant yield or rate of growth. In xe2x80x9cOverproduction of Alfalfa Glutamine Synthetase in Transgenic Tobacco Plantsxe2x80x9d by Peter Eckes et. al., Mol. Gen. Genet. 217, 263 (1989), the authors state that GS overproducing plants were fertile and grew normally, and that a high level of expression of a key metabolic enzyme such as glutamine synthetase does not interfere with growth and fertility of plants. No mention was made of the ratio of leaf-to-root GS activity, which has subsequently been measured by the present inventors to be approximately equal to that for wildtype plants although the activities in both the leaves and the roots have increased.
In xe2x80x9cDoes Root Glutamine Synthetase Control Plant Biomass Production in Lotus Japonicus L.?xe2x80x9d by Anis Limami et al., Planta 209, 495 (1999), the authors show that over expression of root GS activity depresses biomass production. Two transgenic lines that were observed to grow poorly were investigated and the difference in growth between these lines is correlated with the amount of root GS activity; the poorest growth was responsive to the highest GS root activity. Leaf GS activity was observed to remain constant in the plants. Limami et al. do not describe a method for increasing biomass production or increasing plant growth rate or plant dry mass.
Numerous studies of nitrogen metabolism have found that various metabolites are important in the plants regulation of nitrogen metabolism. These compounds include the organic acid malate and the amino acids glutamate and glutamine. Two previous patents have been issued in this general area. In U.S. Pat. No. 5,840,656, for xe2x80x9cMethod for Increasing Fertilizer Efficiencyxe2x80x9d which issued to Alan Kinnersley et. al., on Nov. 24, 1998, an improved fertilizer composition is described that includes conventional fertilizers and an amino acid mixture which includes glutamic acid. U.S. Pat. No. 5,739,082 for xe2x80x9cMethod of Improving the Yield of Herbicide-Resistant Crop Plantsxe2x80x9d which issued to Gunter Donn on Apr. 14, 1998, reports the unexpected improvement in the yield of transgenic crop plants which have been engineered to be resistant to GS inhibitors resulting from the treatment of these plants with very low levels of GS inhibitors. The compound glufosinate [glufosinate-ammonium (ammonium DL-monalanin-4-yl-methyl phosphinate)] acts as a GS inhibitor because it is a structural analog of the GS substrate, glutamic acid. GS is responsible for the detoxification of NH3, and when GS is inhibited by the glufosinate, the plant is severely damaged or destroyed by the toxic accumulation of NH3. No mention is made of the ratio of leaf-to-root GS activity.
The compound, 2-hydroxy-5-oxoproline (also known as 2-oxoglutaramate) is synthesized and metabolized in plants by the sequential action of transaminase and hydrolyase enzymes. Similar transaminase and hydrolyase enzymes and the metabolite, 2-hydroxy-5-oxoproline, have been identified in animal livers and kidneys. These enzymes and the 2-hydroxy-5-oxoproline were partially characterized as described in xe2x80x9cThe Glutamine Transaminase-xcfx89-Amidase Pathwayxe2x80x9d by Arthur L. Cooper and Alton Meister, CRC Critical Reviews in Biochemistry, pages 281-303 (January 1977), and xe2x80x9cEnzymatic Preparation of xcex1-Keto Acidsxe2x80x9d by Alton Meister, J. Biochem. 197, 304 (1952). However, no physiological function was attributed to these compositions in animals.
Accordingly, it is an object of the present invention to improve the properties of plants, including growth rate, fresh weight and dry weight, by increasing the effective quantity of compositions therein to positively affect these properties.
Additional objects, advantages and novel features of the invention will be set forth, in part, in the description that follows, and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects of the present invention, and in accordance with its purposes, as embodied and broadly described herein, the composition hereof includes prolines in an amount effective to increase the rate of growth of plants and improve other properties of growing plants.
In another aspect of the present invention in accordance with its objects and purposes, the method for increasing the rate of growth of plants and for improving other properties of growing plants hereof includes contacting a plant with an effective amount of a proline.
It is preferred that the proline is applied to the foliar portion of the plant.
Preferably, a solution of 2-hydroxy-5-oxoproline (2-oxoglutaramate) is applied to the foliar portion of the plant.
Preferably also 2-hydroxy-5-oxoproline is applied at a rate sufficient to maintain an effective concentration of the proline in the leaf during the growing period of the plant.
Benefits and advantages of the present invention include significant improvement in plant properties, such as growth rate, nodulation, fresh weight and dry weight, with a simple and efficient plant treatment regimen. Similar effects have been observe for algae.